228 BULLETIN OF THE NEW YORK STATE MUSEUM 



III 



DESCRIPTIVE NOTES OF QUARRY DISTRICTS AND 



QUARRIES 



I. Crystalline Rocks 



New York, Manhattan Island. — The outcropping ledges 

 of gneissic rocks, from 29th street (on the ^Yest side) to the 

 Spu^^ten Duyvil creek, and from about i6th street north- 

 wards, on the eastern side of the island. haYe been cut 

 through and graded do^Yn in so man}' places that a large 

 amount of stone has been furnished, ready for laying up 

 foundations and for common wall work. These gneisses 

 are generally bluish-gray in color, medium fine-crystalline, 

 highly micaceous and schistose in structure. The beds are 

 thin and tilted at a high angle and in places are in a verti- 

 cal position. The more micaceous rock is apt to flake 

 and disintegrate on long exposure, especially when the 

 blocks are set on edge. The more feldspathic stone of the 

 granitic veins and dikes and the more hornblendic strata 

 afford a better building material. 



The Croton Reservoir, 5th avenue and 4.26. street and St. 

 Matthew's Lutheran church, Broome street are construc- 

 tions of the best of the island gneiss."^ 



The gneissic rocks have been quarried extensively in the 

 23d and 24th wards. New York cit}^ and in the adjacent 

 southern towns of Westchester county. 



The gray variety of quartzite gneiss has been most 

 largely employed for the better class of building. Geo- 

 logically these gneisses of New York city and the West- 

 chester county quarries are younger than the Laurentian 



*For additionjil examples of the New York island gneiss see tabular statement in 

 Part IV of this report. 



